Vertical transistor fabrication and devices

ABSTRACT

A method of fabricating a vertical field effect transistor including forming a first recess in a substrate; epitaxially growing a first drain from the first bottom surface of the first recess; epitaxially growing a second drain from the second bottom surface of a second recess formed in the substrate; growing a channel material epitaxially on the first drain and the second drain; forming troughs in the channel material to form one or more fin channels on the first drain and one or more fin channels on the second drain, wherein the troughs over the first drain extend to the surface of the first drain, and the troughs over the second drain extend to the surface of the second drain; forming a gate structure on each of the one or more fin channels; and growing sources on each of the fin channels associated with the first and second drains.

BACKGROUND

1. Technical Field

The present invention relates to methods of forming vertical finFETdevices and the electronic device structures produced thereby, and moreparticularly to a method of epitaxially forming the drain, channel, andsource of a vertical finFET such that the drain, channel, and sourcehave the same crystal orientation.

2. Description of the Related Art

A Field Effect Transistor (FET) typically has a source, a channel, and adrain, where current flows from the source to the drain, and a gate thatcontrols the flow of current through the channel. Field EffectTransistors (FETs) can have a variety of different structures, forexample, FETs have been formed with the source, channel, and drainformed in the substrate material itself, where the current flowshorizontally (i.e., in the plane of the substrate), and FinFETs havebeen formed with the channel extending outward from the substrate, butwhere the current also flows horizontally. The channel for the FinFETcan be an upright slab of thin rectangular Si, commonly referred to asthe fin with a gate on the fin, as compared to a MOSFET with a singleplanar gate. Depending on the doping of the source and drain, an n-FETor a p-FET may be formed.

Examples of FETs can include a metal-oxide-semiconductor field effecttransistor (MOSFET) and an insulated-gate field-effect transistor(IGFET). Two FETs also may be coupled to form a complementary metaloxide semiconductor (CMOS), where a p-channel MOSFET and n-channelMOSFET are connected in series.

With ever decreasing device dimensions, forming the individualcomponents and electrical contacts become more difficult. An approach istherefore needed that retains the positive aspects of traditional FETstructures, while overcoming the scaling issues created by formingsmaller device components.

SUMMARY

A method of fabricating a vertical field effect transistor includesforming a first recess in a substrate, wherein the first recess has afirst bottom surface; epitaxially growing a first drain from the firstbottom surface of the first recess; epitaxially growing a second drainfrom the second bottom surface of a second recess formed in thesubstrate; epitaxially growing a channel material on the first drain andthe second drain; forming troughs in the channel material to form one ormore fin channels on the first drain and one or more fin channels on thesecond drain, wherein the troughs over the first drain extend to thesurface of the first drain, and the troughs over the second drain extendto the surface of the second drain; forming a gate structure on each ofthe one or more fin channels; and growing sources on each of the finchannels associated with the first and second drains.

A vertical field effect transistor includes a first recess in asubstrate, wherein the first recess has a first bottom surface. A firstdrain is grown from the first bottom surface of the first recess,wherein the first drain has the same crystal orientation as the firstbottom surface. A second recess is formed in the substrate, wherein thesecond recess has a second bottom surface, and a second drain is grownon the second bottom surface of a second recess formed in the substrate,wherein the second drain has the same crystal orientation as the secondbottom surface. One or more fin channels are formed on the first drain,wherein the one or more fin channels on the first drain have the samecrystal orientation as the first bottom surface, and one or more finchannels are formed on the second drain, wherein the one or more finchannels on the second drain have the same crystal orientation as thesecond bottom surface. A gate structure is formed on each of the finchannels, and sources are grown on each of the fin channels associatedwith the first drain and the second drain, wherein the sources have thesame crystal orientation as the fin channels.

These and other features and advantages will become apparent from thefollowing detailed description of illustrative embodiments thereof,which is to be read in connection with the accompanying drawings.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

The disclosure will provide details in the following description ofpreferred embodiments with reference to the following figures wherein:

FIG. 1 is a cross-sectional view of a substrate for an electronic devicestructure according to an exemplary embodiment;

FIG. 2 is a cross-sectional view of a substrate and a surface layer foran electronic device structure according to an exemplary embodiment;

FIG. 3 is a cross-sectional view of a substrate and a patterned surfacelayer for an electronic device structure according to an exemplaryembodiment;

FIG. 4 is a cross-sectional view of a substrate with etched recesses anda patterned surface layer for an electronic device structure accordingto an exemplary embodiment;

FIG. 5 is a cross-sectional view of a substrate with recessed regionswith a dielectric fill for an electronic device structure according toan exemplary embodiment;

FIG. 6 is a cross-sectional view of a substrate with shallow trenchisolation regions of an electronic device structure according to anexemplary embodiment;

FIG. 7 is a cross-sectional view of a substrate with exposed substrateregions of an electronic device structure according to an exemplaryembodiment;

FIG. 8 is a cross-sectional view of a substrate with exposed substrateregions of an electronic device structure according to an exemplaryembodiment;

FIG. 9 is a cross-sectional view of a substrate with a first drainregion of an electronic device structure according to an exemplaryembodiment;

FIG. 10 is a cross-sectional view of a substrate with a hardmask for anelectronic device structure according to an exemplary embodiment;

FIG. 11 is a cross-sectional view of a substrate with a partiallyremoved hardmask for an electronic device structure according to anexemplary embodiment;

FIG. 12 is a cross-sectional view of a substrate with exposed substrateregions of an electronic device structure according to an exemplaryembodiment;

FIG. 13 is a cross-sectional view of a substrate with exposed substrateregions of an electronic device structure according to an exemplaryembodiment;

FIG. 14 is a cross-sectional view of a substrate with a second drainregion of an electronic device structure according to an exemplaryembodiment;

FIG. 15 is a cross-sectional view of a substrate with a hardmask removedfrom the electronic device structure according to an exemplaryembodiment;

FIG. 16 is a cross-sectional view of a substrate with a channel materialforming the electronic device structure according to an exemplaryembodiment;

FIG. 17 is a cross-sectional view of a substrate with fin channels of anelectronic device structure according to an exemplary embodiment;

FIG. 18 is a cross-sectional view of a substrate with a low-k dielectricmaterial forming the electronic device structure according to anexemplary embodiment;

FIG. 19 is a cross-sectional view of a substrate with a low-k dielectricmaterial forming the electronic device structure according to anexemplary embodiment;

FIG. 20 is a cross-sectional view of a substrate with a low-k dielectricmaterial forming the electronic device structure according to anexemplary embodiment;

FIG. 21 is a cross-sectional view of a substrate with a WFM layer of anelectronic device structure according to an exemplary embodiment;

FIG. 22 is a cross-sectional view of a substrate with WFM caps of anelectronic device structure according to an exemplary embodiment;

FIG. 23 is a cross-sectional view of a substrate with gate materialforming an electronic device structure according to an exemplaryembodiment;

FIG. 24 is a cross-sectional view of a substrate with a reduced heightgate material forming an electronic device structure according to anexemplary embodiment;

FIG. 25 is a cross-sectional view and enlarged inset view of a substratewith a reduced height gate material forming an electronic devicestructure according to an exemplary embodiment;

FIG. 26 is an enlarged inset cross-sectional view of a substrate with areduced height gate material forming an electronic device structureaccording to an exemplary embodiment;

FIG. 27 is an enlarged inset cross-sectional view of a substrate with areduced height gate precursor and WFM cap forming an electronic devicestructure according to an exemplary embodiment;

FIG. 28 is an enlarged inset cross-sectional view of a substrate with adisposable spacer forming an electronic device structure according to anexemplary embodiment;

FIG. 29 is an enlarged inset cross-sectional view of a substrate with adisposable spacer forming an electronic device structure according to anexemplary embodiment;

FIG. 30 is an enlarged inset cross-sectional view of a substrate with adisposable spacer forming an electronic device structure according to anexemplary embodiment;

FIG. 31 is an enlarged inset cross-sectional view of a substrate with anexposed fin channel and a gate structure forming an electronic devicestructure according to an exemplary embodiment;

FIG. 32 is an enlarged inset cross-sectional view of a substrate with agate structure and low-k dielectric material forming an electronicdevice structure according to an exemplary embodiment;

FIG. 33 is an enlarged inset cross-sectional view of a substrate with agate structure and low-k dielectric material forming an electronicdevice structure according to an exemplary embodiment;

FIG. 34 is a cross-sectional view of a substrate with low-k dielectricspacers and exposed fin channels of an electronic device structureaccording to an exemplary embodiment;

FIG. 35 is a cross-sectional view of a substrate with an inter-layerdielectric of an electronic device structure according to an exemplaryembodiment;

FIG. 36 is a cross-sectional view of a substrate with an inter-layerdielectric and hardmask of an electronic device structure according toan exemplary embodiment;

FIG. 37 is a cross-sectional view of a substrate with an inter-layerdielectric and a partially removed hardmask of an electronic devicestructure according to an exemplary embodiment;

FIG. 38 is a cross-sectional view of a substrate with an inter-layerdielectric and sources of an electronic device structure according to anexemplary embodiment;

FIG. 39 is a cross-sectional view of a substrate with an inter-layerdielectric and removed hardmask of an electronic device structureaccording to an exemplary embodiment;

FIG. 40 is a cross-sectional view of a substrate with an inter-layerdielectric and a partially removed hardmask of an electronic devicestructure according to an exemplary embodiment;

FIG. 41 is a cross-sectional view of a substrate with an inter-layerdielectric and sources of an electronic device structure according to anexemplary embodiment;

FIG. 42 is a cross-sectional view of a substrate with an inter-layerdielectric and removed hardmask of an electronic device structureaccording to an exemplary embodiment;

FIG. 43 is a cross-sectional top view of a substrate with a drain and aplurality of fin channels of an electronic device structure according toan exemplary embodiment;

FIG. 44 is a cross-sectional top view of a substrate with draincontacts, gate contacts, and source contacts of an electronic devicestructure according to an exemplary embodiment;

FIG. 45 is a cross-sectional side view of a fin channel assembly withdrain contacts, gate contacts, and source contacts of an electronicdevice structure according to an exemplary embodiment;

FIG. 46 is a cross-sectional side view of a fin channel assembly showingmultiple layers of an electronic device structure according to anexemplary embodiment;

FIG. 47 is a block/flow diagram of an exemplary method of forming avertical finFET in accordance with an illustrative embodiment;

FIG. 48 is a continuation of the block/flow diagram of an exemplarymethod of forming a vertical finFET of FIG. 47 in accordance with anillustrative embodiment;

FIG. 49 is a continuation of the block/flow diagram of an exemplarymethod of forming a vertical finFET of FIG. 48 in accordance with anillustrative embodiment;

FIG. 50 is a continuation of the block/flow diagram of an exemplarymethod of forming a vertical finFET of FIG. 49 in accordance with anillustrative embodiment;

FIG. 51 is a continuation of the block/flow diagram of an exemplarymethod of forming a vertical finFET of FIG. 50 in accordance with anillustrative embodiment;

FIG. 52 is a continuation of the block/flow diagram of an exemplarymethod of forming a vertical finFET of FIG. 51 in accordance with anillustrative embodiment; and

FIG. 53 is a continuation of the block/flow diagram of an exemplarymethod of forming a vertical finFET of FIG. 52 in accordance with anillustrative embodiment.

DETAILED DESCRIPTION

Principle and embodiments of the present disclosure relate to asemiconductor device structure with conductive elements stacked on thesubstrate to form a conductive path normal to the surface of thesubstrate on which the semiconductor structure is formed. An embodimentrelates generally to a vertical finFET structure that provides enhancedgeometries for electrical contact formation and current carryingproperties. In an embodiment, a finFET semiconductor device has thedrain, fin channel, and source device components arranged perpendicularto the plane of the substrate surface, which is referred to as avertical stack. A vertically stacked finFET can have a longer gatelength (i.e., height) and larger dielectric spacer than a horizontal(i.e., having the drain, fin channel, and source device componentsarranged parallel with the plane of the substrate surface) finFET havingcomparable contact gate pitch.

In one or more embodiments, a source, drain, and channel of a finFET aregrown epitaxially on a crystalline substrate. In various embodiments, asource or drain is formed epitaxially directly on the substrate and thea fin channel is epitaxially formed directly on the source or drain,where the substrate, drain, fin channel, and source all have the samecrystal structure and orientation.

It is to be understood that the present invention will be described interms of a given illustrative architecture; however, otherarchitectures, structures, substrate materials and process features andsteps may be varied within the scope of the present invention.

It will also be understood that when an element such as a layer, regionor substrate is referred to as being “on” or “over” another element, itcan be directly on the other element or intervening elements may also bepresent. In contrast, when an element is referred to as being “directlyon” or “directly over” another element, there are no interveningelements present. It will also be understood that when an element isreferred to as being “connected” or “coupled” to another element, it canbe directly connected or coupled to the other element or interveningelements may be present. In contrast, when an element is referred to asbeing “directly connected” or “directly coupled” to another element,there are no intervening elements present.

The present embodiments may include a design for an integrated circuitchip, which may be created in a graphical computer programming language,and stored in a computer storage medium (such as a disk, tape, physicalhard drive, or virtual hard drive such as in a storage access network).If the designer does not fabricate chips or the photolithographic masksused to fabricate chips, the designer may transmit the resulting designby physical means (e.g., by providing a copy of the storage mediumstoring the design) or electronically (e.g., through the Internet) tosuch entities, directly or indirectly. The stored design is thenconverted into the appropriate format (e.g., GDSII) for the fabricationof photolithographic masks, which typically include multiple copies ofthe chip design in question that are to be formed on a wafer. Thephotolithographic masks are utilized to define areas of the wafer(and/or the layers thereon) to be etched or otherwise processed.

Methods as described herein may be used in the fabrication of integratedcircuit chips. The resulting integrated circuit chips can be distributedby the fabricator in raw wafer form (that is, as a single wafer that hasmultiple unpackaged chips), as a bare die, or in a packaged form. In thelatter case the chip is mounted in a single chip package (such as aplastic carrier, with leads that are affixed to a motherboard or otherhigher level carrier) or in a multichip package (such as a ceramiccarrier that has either or both surface interconnections or buriedinterconnections). In any case the chip is then integrated with otherchips, discrete circuit elements, and/or other signal processing devicesas part of either (a) an intermediate product, such as a motherboard, or(b) an end product. The end product can be any product that includesintegrated circuit chips, ranging from toys and other low-endapplications to advanced computer products having a display, a keyboardor other input device, and a central processor.

It should also be understood that material compounds will be describedin terms of listed elements, e.g., SiN, GaAs or SiGe. These compoundsinclude different proportions of the elements within the compound, e.g.,GaAs includes Ga_(x)As_(1-x), where x is less than or equal to 1, orSiGe includes Si_(x)Ge_(1-x) where x is less than or equal to 1, etc. Inaddition, other elements may be included in the compound, such as, e.g.,AlInGaAs, and still function in accordance with the present principles.The compounds with additional elements will be referred to herein asalloys.

Reference in the specification to “one embodiment” or “an embodiment” ofthe present principles, as well as other variations thereof, means thata particular feature, structure, characteristic, and so forth describedin connection with the embodiment is included in at least one embodimentof the present principles. Thus, the appearances of the phrase “in oneembodiment” or “in an embodiment”, as well any other variations,appearing in various places throughout the specification are notnecessarily all referring to the same embodiment.

It is to be appreciated that the use of any of the following “/”,“and/or”, and “at least one of” for example, in the cases of “A/B”, “Aand/or B” and “at least one of A and B”, is intended to encompass theselection of the first listed option (A) only, or the selection of thesecond listed option (B) only, or the selection of both options (A andB). As a further example, in the cases of “A, B, and/or C” and “at leastone of A, B, and C”, such phrasing is intended to encompass theselection of the first listed option (A) only, or the selection of thesecond listed option (B) only, or the selection of the third listedoption (C) only, or the selection of the first and the second listedoptions (A and B) only, or the selection of the first and third listedoptions (A and C) only, or the selection of the second and third listedoptions (B and C) only, or the selection of all three options (A and Band C). This may be extended, as readily apparent by one of ordinaryskill in this and related arts, for as many items listed.

In one or more embodiments, a front end process for building verticalfinFETs includes several process modules to prepare building blocks ofthe finFET, where separate device components are formed by each processmodule.

In various embodiments, the device components have a smallest ornarrowest dimension of <10 nm, although other node sizes are alsocontemplated.

Referring now to the drawings in which like numerals represent the sameor similar elements and initially to FIG. 1, which is a diagram of asubstrate for an electronic device structure according to an exemplaryembodiment. The diagram shows a cross-sectional view illustrating the xand z directions of the device structure.

In various embodiments, a substrate 100 may be a semiconductor. Thesubstrate may be crystalline. The substrate may be primarily (i.e., withdoping) of a single element, for example, silicon (Si) or germanium,(Ge), or the substrate may be a compound, for example, GaAs, SiC, orSiGe. The substrate may also have multiple material layers, for example,a semiconductor-on-insulator substrate (SeOI), a silicon-on-insulatorsubstrate (SOI), germanium-on-insulator substrate (GeOI), orsilicon-germanium-on-insulator substrate (SGOI). The substrate may alsohave other layers forming the substrate, including high-k oxides and/ornitrides. In one or more embodiments, the substrate 100 may be a siliconwafer. In an embodiment, the substrate is a single crystal siliconwafer.

An exposed surface 110 of substrate 100 may be a material different fromthe bulk or body of the substrate 100, or may be a component-richsurface of a compound material, for example, a silicon-rich orgermanium-rich layer of a SiGe substrate, a gallium-rich layer of a GaAssubstrate, or a nitrogen-rich surface of a GaN layer, where the exposedsurface may be one of two altering atomic layers. In variousembodiments, the substrate may have a graded concentration, where forexample, the exposed material at the surface of the substrate isprimarily silicon with a predetermined crystal orientation suitable forepitaxial growth, whereas the bulk material may comprise other chemicalelements, for example, germanium. In various embodiments, the thicknessof the single crystal material at the surface 110 may be greater thanabout 200 nm thick, or greater than about 300 nm thick, or greater thanabout 500 nm thick. For example, an SOI substrate may have a singlecrystal silicon surface layer about 300 nm thick above the insulatinglayer.

In various embodiments, a doped material has impurity concentration inthe range of parts-per-billion to parts-per-thousand, or morespecifically from about 10¹³ cm⁻³ to about 10¹⁸ cm⁻³. In contrast, aformula of Si_(x)Ge_(1-x) represents concentrations of at least an orderof magnitude greater than doping levels, or more specifically,0.005≦x≦0.995.

In various embodiments, the substrate may include variousheterostructures.

The exposed surface 110 of a substrate 100 may be prepared by, forexample, cleaning, chemical-mechanical polishing (CMP), planarizing,annealing, etching/defect removal, and/or oxide removal for subsequentprocessing steps including but not limited to masking, etching,deposition, implantation, and thermal activation.

FIG. 2 is a diagram of a substrate and a surface layer for an electronicdevice structure according to an exemplary embodiment. The diagram showsa cross-sectional view illustrating the x and z directions of the devicestructure.

In various embodiments, a layer 200 may be formed on the exposed surface110 of substrate 100. The layer 200 may be a material different from thematerial of the substrate 100, or the material at the exposed surface110. The layer 200 and exposed surface 110 of substrate 100 may form aninterface 120, where the layer 200 and exposed surface 110 are incontact. The layer 200 may be continuous and uniform over at least aportion of the substrate surface 110.

The layer 200 may have a thickness, where the thickness may be in therange of about 20 Å to about 500 Å, or about 30 Å to about 300 Å, orabout 50 Å to about 250 Å.

In various embodiments, layer 200 may be deposited by physical vapordeposition (PVD), chemical vapor deposition (CVD), atomic layerdeposition (ALD), or any of the various modifications thereof, forexample plasma-enhanced chemical vapor deposition (PECVD), metal-organicchemical vapor deposition (MOCVD), low pressure chemical vapordeposition (LPCVD), electron-beam physical vapor deposition (EB-PVD),and plasma-enhanced atomic layer deposition (PE-ALD). In one or moreembodiments, layer 200 is deposited by PECVD or LPCVD. The depositionsmay be epitaxial processes, and the deposited material may becrystalline. In various embodiments, formation of a layer may be by oneor more deposition processes, where, for example, a conformal layer maybe formed by a first process (e.g., ALD, PE-ALD, etc.) and a fill may beformed by a second process (e.g., CVD, electrodeposition, PVD, etc.

FIG. 3 is a diagram of a substrate and a patterned surface layer for anelectronic device structure according to an exemplary embodiment. Thediagram shows a cross-sectional view illustrating the x and z directionsof the device structure.

In one or more embodiments, portions of layer 200, which may be made ofan insulator material that provides a mask for etching of the substrate100, and may be removed, for example by masking and wet etching orreactive ion etching (RIE) to form islands 220 of the material of layer200 on the substrate 100. It should be noted that not all masking,patterning, and lithography processes are shown, since a person ofordinary skill in the art would recognize where masking and patterningare utilized to form the identified layers and openings, and to performthe identified selective etching processes, as described herein. Thelayer 200 may be a nitride, for example silicon nitride (SiN) ortitanium nitride (TiN) to form a mask with exposed regions betweenislands 220. In one or more embodiments, layer 200 is a Si₃N₄ layer toprovide for selective etching of Si. In various embodiments, portions oflayer 200 are removed to form islands 220 having sizes in the range ofabout 100 nm² to about 100,000 nm², or in the range of about 1,000 nm²to about 50,000 nm², or in the range of about 5,000 nm² to about 10,000nm². The areas 230 between the islands 220, may have dimensions in therange of about 500 nm by about 500 nm, or in the range of about 250 nmby about 250 nm, or in the range of about 100 nm by about 100 nm, orabout 60 nm by about 60 nm, where the area may be square or rectangular.In various embodiments, the areas between the islands may have a surfacearea in the range of about 3600 nm² to about 250,000 nm², where the areamay be rectangular.

FIG. 4 is a diagram of a substrate with etched recesses and a patternedsurface layer for an electronic device structure according to anexemplary embodiment. The diagram shows a cross-sectional viewillustrating the x and z directions of the device structure.

In one or more embodiments, a portion of the substrate 100 may be etchedto form recessed regions 150 within the substrate 100, where therecessed regions 150 may be utilized to form shallow trench isolation(STI) regions.

FIG. 5 is a diagram of a substrate with recessed regions with adielectric fill for an electronic device structure according to anexemplary embodiment. The diagram shows a cross-sectional viewillustrating the x and z directions of the device structure.

A dielectric material layer 300 may be deposited over the substrate 100and islands 220 to fill in the recessed regions 150 of the substrate100. In various embodiments, the dielectric material layer 300 may besilicon oxide (SiO₂), silicon oxinitride (SiON), or silicon nitride(SiN), where the chemical composition of the dielectric material layer300 is different from the chemical composition of the islands 220. Thedifference in the material of islands 220 and dielectric material layer300 may provide selective etching rates and/or an etch stop. In variousembodiments, the thickness of the deposited dielectric material layer300 is sufficient to cover the recessed regions 150 and the islands 220,where the height of the dielectric material layer 300 above the recessedregion is greater than the height of the substrate and islands 220 abovea lowest surface 155 of the recessed regions 150. The dielectricmaterial layer 300 may be conformally deposited in recessed regions 150.

FIG. 6 is a diagram of a substrate with shallow trench isolation (STI)regions of an electronic device structure according to an exemplaryembodiment. The diagram shows a cross-sectional view illustrating the xand z directions of the device structure.

The dielectric material layer 300 may be etched back and/orchemically-mechanically polished to form a planar surface 350. Therecessed regions 150 filled with the dielectric material layer 300, andbounded by the lowest surface 155 of the recessed regions 150, planarsurface 350, and the side walls 180 of substrate 100 and islands 220form the shallow trench isolation regions 330. In various embodiments,the dielectric material layer 300 may be a deposited SiO₂ layer. Thethickness of the islands may be greater than the final thickness toallow the surface of islands 220 to be etched or polished back to afinal thickness. The STI regions 330 separate the islands 220, andprovide electrical insulation between the substrate areas below theislands 220.

FIG. 7 is a diagram of a substrate with exposed substrate regions of anelectronic device structure according to an exemplary embodiment. Thediagram shows a cross-sectional view illustrating the x and z directionsof the device structure.

In one or more embodiments, an island 220 may be removed by etching toexpose an underlying portion of substrate 100, while other islands 220remain on the substrate. Selective etching of one or more islands may beaccomplished by wet etching or reactive ion etching. A mask may beformed over specific islands 220 to allow selective removal of one ormore islands in one or more separate etching steps.

FIG. 8 is a diagram of a substrate with exposed substrate regions of anelectronic device structure according to an exemplary embodiment. Thediagram shows a cross-sectional view illustrating the x and z directionsof the device structure.

In various embodiments, the substrate 100 below the previously removedisland(s) 220 may be etched to decrease the height of the substrate andincrease the depth of the first recess 170 between two shallow trenchisolation regions 330. The exposed substrate surface 190 at the bottomof first recess 170 (i.e., the first bottom surface) may be suitable forepitaxial growth. The exposed substrate surface 190 may be cleaned andprepared for the epitaxial growth of a drain material or a sourcematerial. While embodiments are described with a drain region formed onthe substrate, this is for descriptive purposes only and should not beconstrued as a limitation, as a source region formed on the substrate iscontemplated as within the inventive scope.

In various embodiments, the final recess depth of the substrate surfaceis less than the depth of the adjacent STI regions. The shallow trenchisolation regions 330 may have a depth in the range of about 10 nm toabout 300 nm, or in the range of about 25 nm to about 250 nm, or in therange of about 50 nm to about 200 nm.

FIG. 9 is a diagram of a substrate with a first drain region of anelectronic device structure according to an exemplary embodiment. Thediagram shows a cross-sectional view illustrating the x and z directionsof the device structure.

In one or more embodiments, a first drain 400 is formed on the surface190 of the substrate 100 between shallow trench isolation regions 330.The first drain 400 may be epitaxially grown on the surface 190 by CVD,PE-CVD, ALD, PE-ALD, or combinations thereof, and have the crystalorientation of the substrate.

In one or more embodiments, a first drain 400 may be silicon (Si),silicon carbide (SiC), or silicon germanium (Si_(x)Ge_(y)). In variousembodiments, first drain 400 may be doped with boron, phosphorus, orcarbon to form an n-FET or a p-FET. In one or more embodiments, thefirst drain 400 may be boron-doped silicon germanium (SiGe—B) orphosphorus-doped silicon carbide (SiC—P). In an embodiments, an n-FET ifformed using SiGe, and a p-FET is formed using SiC. In variousembodiments, arsenic is not used as a dopant.

In various embodiments, first drain 400 may have a thickness in therange of about 10 nm to about 250 nm, or about 20 nm to about 150 nm, orabout 50 nm to about 100 nm. The interface between the substrate 100 andthe bottom surface of the first drain 400 can be above the interfacebetween the substrate 100 and the bottom surface of the STI region(s)330, where the STI regions 330 may be the STI regions adjacent to thefirst drain 400. In various embodiments, dopants may be added to thefirst drain 400 in-situ during the epitaxial growth of the drain, orex-situ by an ion implantation technique. The dopant concentrationwithin <5 nm of the first drain surface may be essentially free (i.e.,approximately zero concentration) to enable channel epitaxial growth onthe exposed surface of the drain 400.

FIG. 10 is a diagram of a substrate with a hardmask for an electronicdevice structure according to an exemplary embodiment. The diagram showsa cross-sectional view illustrating the x and z directions of the devicestructure.

A hardmask 500 may be formed over the first drain 400, shallow trenchisolation regions 330, and islands 220. In various embodiments, thehardmask 500 may be an oxide, boride, carbide, or a nitride, where thehardmask 500 is compatible with the drain material. In variousembodiments, the hardmask is silicon nitride.

FIG. 11 is a diagram of a substrate with a partially removed hardmaskfor an electronic device structure according to an exemplary embodiment.The diagram shows a cross-sectional view illustrating the x and zdirections of the device structure.

The hardmask 500 may be removed from one or more islands 220 to exposethe one or more islands 220 for removal, while protecting first drain400. Portions of the hardmask 500 may be removed by selectively maskingand etching.

FIG. 12 is a diagram of a substrate with exposed substrate regions of anelectronic device structure according to an exemplary embodiment. Thediagram shows a cross-sectional view illustrating the x and z directionsof the device structure.

The island(s) 220 may be removed, where the island material may be wetetched or dry etched to expose the underlying substrate 100.

FIG. 13 is a diagram of a substrate with exposed substrate regions of anelectronic device structure according to an exemplary embodiment. Thediagram shows a cross-sectional view illustrating the x and z directionsof the device structure.

In various embodiments, the substrate 100 below the previously removedisland 220 may be etched to decrease the height of the substrate andincrease the depth of the second recess 175 between two shallow trenchisolation regions 330. After etching, the height of the substrate may beabove the interface between the substrate 100 and the neighboring STIregions 330. The exposed substrate surface 195 at the bottom of secondrecess 175 (i.e., the second bottom surface) may be suitable forepitaxial growth. The exposed substrate surface 195 may be cleaned andprepared for the epitaxial growth of a drain material or a sourcematerial.

FIG. 14 is a diagram of a substrate with a second drain region of anelectronic device structure according to an exemplary embodiment. Thediagram shows a cross-sectional view illustrating the x and z directionsof the device structure.

In one or more embodiments, a second drain 600 is formed on the secondbottom surface 195 of the substrate 100 between shallow trench isolationregions 330. The second drain 600 may be epitaxially grown on thesurface 190 by CVD, PE-CVD, ALD, PE-ALD, or combinations thereof, andhave the crystal orientation of the substrate.

In one or more embodiments, a second drain 600 may be silicon (Si),silicon carbide (SiC), or silicon germanium (Si_(x)Ge_(y)). In variousembodiments, second drain 600 may be doped with boron, phosphorus, orcarbon to form an n-FET or a p-FET. In one or more embodiments, thesecond drain 600 may be boron-doped silicon germanium (SiGe—B) orphosphorus-doped silicon carbide (SiC—P). In various embodiments,arsenic is not used as a dopant for the drain(s).

In various embodiments, second drain 600 may be made of a differentmaterial and/or doped with a different material than first drain 400.The second drain 600 may be an n-type material and first drain 400 maybe a p-type material, or second drain 600 may be an p-type material andfirst drain 400 may be a n-type material.

In various embodiments, second drain 600 may have a thickness in therange of about 10 nm to about 250 nm, or about 20 nm to about 150 nm, orabout 50 nm to about 100 nm. The interface between the substrate 100 andthe bottom surface of the second drain 600 can be above the interfacebetween the substrate 100 and the bottom surface of the STI region 330,where the STI regions 330 may be the STI regions adjacent to the seconddrain 600. In various embodiments, dopants may be added to the seconddrain 600 in-situ during the epitaxial growth of the second drain, orex-situ by an ion implantation technique. The dopant concentrationwithin <5 nm of the surface of the second drain 600 may be essentiallyfree (i.e., approximately zero concentration) to enable epitaxialchannel growth on the exposed surface of the drain 600. The first drain400 and the second drain 600 may have the same height or differentheights. The STI regions 330 may separate first drain 400 from seconddrain 600 and provide electrical insulation between drain 400 and drain600.

FIG. 15 is a diagram of a substrate with a hardmask removed from theelectronic device structure according to an exemplary embodiment. Thediagram shows a cross-sectional view illustrating the x and z directionsof the device structure.

The hardmask 500 may be removed from second drain 600 and shallow trenchisolation regions 330 by etching. The exposed surfaces of first drain400 and second drain 600 may be prepared for epitaxial growth of achannel material by cleaning and/or thermal treatment.

FIG. 16 is a diagram of a substrate with a channel material forming theelectronic device structure according to an exemplary embodiment. Thediagram shows a cross-sectional view illustrating the x and z directionsof the device structure.

In one or more embodiments, a channel material 700 is formed on at leasta first drain 400 and a second drain 600. The channel material 700 maybe grown epitaxially to extend above the top surface(s) of STI regions330, where excess channel material 700 may be etched orchemically-mechanically polished to provide a smooth, flat surface 710,where the surface 710 of the channel material 700 may be suitable forepitaxial growth.

In one or more embodiments, the channel material 700 may be intrinsicSi, Si_(x)Ge_(y), GaAs, and InGaAs. The channel material may beepitaxially grown on the exposed surface of first drain 400 and/orsecond drain 600, where a channel material/drain interface may be formedbetween drain 400 and/or drain 600 and the channel material. The channelmaterial may be grown simultaneously on first drain 400 and second drain600. In various embodiments, the interface 720 may have particularelectronic properties, for example, improved carrier mobility andtransport characteristics, based on the crystal structure andorientation of first drain 400 and/or second drain 600, for example, adeposited Si_(x)Ge_(y) may be strained due to crystal lattice mismatchat the channel material/drain interface 720.

FIG. 17 is a diagram of a substrate with fin channels of an electronicdevice structure according to an exemplary embodiment. The diagram showsa cross-sectional view illustrating the x and z directions of the devicestructure.

The channel material may be masked and/or etched to produce troughs 740between a plurality of channel fins 750, where the channel fins 750 maybe pillars with a proximal end adjacent the surface of a first drain 400or second drain 600 and extending perpendicularly from the surface offirst drain 400 or second drain 600. The troughs 740 may be formedbetween the fin channels 750 by RIE. The channel fins 750 may, thereby,be associated with the first drain or with the second drain.

In various embodiments, a single section of channel material 700 may beetched to produce from 1 to 25 fin channels, or 1 to 15 fin channels, or1 to 10 fin channels, 2 to 10 fin channels, or 1 to 5 fin channels, or 2to 5 fin channels, or 2-3 fin channels. The size of the section ofchannel material 700 may be based on the predetermined number of finchannels to be formed from the section of channel material, where thesize of the section of channel material is determined by the size of thefirst drain 400 or second drain 600, which depends on the size of theislands 220. In various embodiments, a plurality of fin channels 750extend from the same drain 400 or from the same drain 600, such thatcurrent passing through first drain 400 or second drain 600 isdistributed to the plurality of fin channels 750 formed thereon.

In embodiments in which a single fin channel is formed on first drain400 or second drain 600, troughs 740 may be formed between the sides offin channel 750 and side walls of STI regions 330. In embodiments inwhich multiple fin channels 750 are formed on first drain 400 or seconddrain 600, troughs 740 may be formed between the sides of fin channel750 facing the side walls of the STI regions 330.

The height of the fin channel 750 in the z direction may be in the rangeof about 30 nm to about 400 nm, or in the range of about 50 nm to about300 nm, or in the range of about 75 nm to about 200 nm. In variousembodiments, the width of the fin channel 750 in the x direction may bein the range of about 5 nm to about 30 nm, or about 10 nm to about 20nm. In various embodiments, the aspect ratio of the fin channel 750 maybe in the range of about 3 to about 40, or in the range of about 5 toabout 20, or in the range of about 7 to about 10. In variousembodiments, the fin channel 750 may have a length in the y direction inthe range of about 10 nm to about 2000 nm, or in the range of about 20nm to about 1000 nm, or in the range of about 25 nm to about 500 nm,where the length in the y direction is greater than the width in the xdirection. In a non-limiting example, a fin channel 750 may have a widthin the x direction of 5 nm, a length in the y direction of 100 nm, and aheight in the z direction of about 200 nm.

The number and size of fin channels 750 to be formed may be based on theintended current handling capacity of the electronic device structure.The number and size of the fin channels is correlated with the size ofthe islands 200, where more or larger fin channels 750 may be formed onlarger area drains.

FIG. 18 is a diagram of a substrate with a low-k dielectric materialforming the electronic device structure according to an exemplaryembodiment. The diagram shows a cross-sectional view illustrating the xand z directions of the device structure.

On one or more embodiments, a first low-k dielectric material 800 isformed over the fin channels 750 and in the troughs 740 to form low-kspacers isolating the channel fins 750. The first low-k dielectricmaterial 800 may bury the shallow trench isolation regions 330. Invarious embodiments, the first low-k spacer material may be SiBCN,SiOCN, SiN or combinations thereof.

FIG. 19 is a diagram of a substrate with a low-k dielectric materialforming the electronic device structure according to an exemplaryembodiment. The diagram shows a cross-sectional view illustrating the xand z directions of the device structure.

A portion of the first low-k dielectric material 800 may be removed bychemical-mechanical polishing to provide a flat, uniform surface 810.The height of the first low-k dielectric material 800 may be reduced tothe height of the fin channels 750 by chemical-mechanical polishing toform a smooth planar surface.

FIG. 20 is a diagram of a substrate with a low-k dielectric materialforming the electronic device structure according to an exemplaryembodiment. The diagram shows a cross-sectional view illustrating the xand z directions of the device structure.

The first low-k dielectric material 800 may be removed to apredetermined depth leaving at least a portion of the fin channels 750exposed above the first low-k dielectric spacers 820. In variousembodiments, the top surface of the first low-k dielectric spacer 820 isco-planar with the top surface of the shallow trench isolation regions330. The first low-k dielectric spacer(s) 820 may be adjacent to atleast a portion of each of the fin channels 750.

In various embodiments, a work function metal (WFM) layer 900 is formedover exposed portions of the fin channels 750, STI region 330, and firstlow-k dielectric spacers 820, where the work function metal layer 900may be conformally deposited. The WFM may include multiple depositedlayers. In various embodiments, the WFM layer 900 may be deposited byALD or PE-ALD.

In various embodiments the WFM layer 900 is composed of at least onehigh-k oxide layer and at least one gate metal layer, where the high-koxide may be HfO₂, HfSiO₄, HfSiON, La₂O₃, Ta₂O₅, ZrO₂, and/or SrTiO₃, orcombinations thereof, and the gate metal may be TiN, HfN, TaN, TiC, TaC,HfC, WC, TiAlN, or combinations thereof, where the WFM layer 900 mayhave multiple material layers. In various embodiments, the gate metalmay be a metal nitride, where the metal nitride may be TiN, HfN, TaN,TiAlN, or combinations thereof. In various embodiments, a WFMinter-layer dielectric (ILD) is the high-k oxide formed prior to thegate metal. In one or more embodiments, the high-k oxide layer isadjacent to the fin channel 750 and forms an interface with the verticalside surfaces of the fin channel 750. A high-k oxide layer may be formedbefore the gate metal layer, where the high-k oxide layer is directly onat least a portion of fin channel 750.

FIG. 21 is a diagram of a substrate with a WFM layer of an electronicdevice structure according to an exemplary embodiment. The diagram showsa cross-sectional view illustrating the x and z directions of the devicestructure.

The work function metal layer 900 may be selectively removed to leavework function metal caps 920 on the exposed top and side surfaces of thefin channels 750. The WFM layer 900 may be removed by masking andetching each of the high-k oxide and metal nitride materials. In variousembodiments, the work function metal caps 920 may have a thickness ofless than about 15 nm, where the thickness of the WFM cap 920 is a sumof at least one high-k oxide layer thickness and the at least one metalnitride layer thickness.

FIG. 22 is a diagram of a substrate with WFM caps of an electronicdevice structure according to an exemplary embodiment. The diagram showsa cross-sectional view illustrating the x and z directions of the devicestructure.

The top portion of the work function metal caps 920 may be removed byetching or polishing to reveal the tops of the fin channels 750 leavingthe sides of the WFM cap 920 on each side of the fin channels 750. Invarious embodiments, the WFM caps 920 may have a thickness in the rangeof about 5 nm to about 15 nm, or a thickness in the range of about 7 nmto about 10 nm, or a thickness of about 7 nm.

FIG. 23 is a diagram of a substrate with gate material forming anelectronic device structure according to an exemplary embodiment. Thediagram shows a cross-sectional view illustrating the x and z directionsof the device structure.

A gate material 1000 may be formed over the tops of the fin channels 750and work function metal caps 920, where the gate material 1000 fills inthe troughs 740 between the WFM caps 920 and between the WFM caps 920and STI regions 330. The STI regions 330 and the first low-k dielectricspacers 820 may be buried beneath the gate material 1000. In variousembodiments, the gate material 1000 is a metal, where the metal may betungsten (W), tungsten nitride (WN) or combinations thereof. In one ormore embodiments, the gate material 1000 is tungsten (W). The gatematerial 1000 may be deposited by CVD or PE-CVD.

In one or more embodiments, the gate material 1000 and WFM cap 920 isseparated from the first drain 400 and/or second drain 600 by the firstlow-k dielectric spacers 820, which may also provide isolation of thefirst drain 400 and/or second drain 600 from the conducting layers ofthe gate material 1000 and WFM cap 920.

FIG. 24 is a diagram of a substrate with a reduced height gate materialforming an electronic device structure according to an exemplaryembodiment. The diagram shows a cross-sectional view illustrating the xand z directions of the device structure.

A portion of the gate material 1000 may be removed bychemical-mechanical polishing to provide a flat, uniform surface, wherethe top surface of the gate material 1000 may be coplanar with the topsurfaces of the fin channels 750.

FIG. 25 is a diagram and enlarged inset view of a substrate with areduced height gate material forming an electronic device structureaccording to an exemplary embodiment. The diagram shows across-sectional view illustrating the x and z directions of the devicestructure.

The gate material 1000 may be removed to a predetermined depth leavingat least a portion of the fin channels 750 exposed above the gatematerial 1000. A height of gate material is left to form gate precursors1020. In various embodiments the height of the gate precursors 1020above the surface of the low-k dielectric spacer 820 may be in the rangeof about 15 nm to about 300 nm, or about 15 nm to about 100 nm, or about15 nm to about 50 nm. In various embodiments, the height of the gateprecursor 1020 in the z direction is related to height of the finchannel, where the height of the gate precursor is less than the heightof the of the fin channel 750 in the z direction. In variousembodiments, the height of the gate precursor 1020 may be less than orequal to the height of the WFM cap 920, where the height of the WFM cap920 may be subsequently reduced to be about equal with the height of thegate precursor 1020.

FIG. 26 is an enlarged inset view of a substrate with a reduced heightgate material forming an electronic device structure according to anexemplary embodiment. The diagram shows a cross-sectional viewillustrating the x and z directions of the device structure.

The enlarged inset view of FIG. 25 illustrating a drain and fin channelassembly is also shown in FIG. 26. The inset shows three fin channelsextending from and electrically coupled to the same first drain 400, andWFM caps 920 with a greater height than the gate precursors 1020. TheWFM cap electrically separates the gate precursor 1020 from the finchannel 750. WFM caps 920 and gate precursors 1020 are insulated fromfirst drain 400 by the first low-k dielectric spacers 820 and STIregion(s) 330. The tungsten of the gate precursor 1020 is isolated fromthe fin channel 750 by the high-k dielectric layer of the WFM caps 920.

FIG. 27 is an enlarged inset view of a substrate with a reduced heightgate precursor and WFM cap forming an electronic device structureaccording to an exemplary embodiment. The diagram shows across-sectional view illustrating the x and z directions of the devicestructure.

In various embodiments, the WFM cap 920 above the level of the gateprecursor 1020 may be removed to expose the sidewalls of the fin channel750 above the top surface of the gate precursor 1020, where the WFM cap920 may be removed by etching. After removal of the portions of the WFMcaps 920 extending above the gate precursor 1020, the WFM caps 920 andgate precursor 1020 may have about the same height. In variousembodiments, the fin channel 750 extends about 25 nm to about 100 nmabove the WFM caps 920 and gate precursor 1020, or in the range of about35 nm to about 75 nm above the WFM caps 920 and gate precursor 1020.

FIG. 28 is an enlarged inset view of a substrate with a disposablespacer forming an electronic device structure according to an exemplaryembodiment. The diagram shows a cross-sectional view illustrating the xand z directions of the device structure.

A disposable spacer material 1100 may be formed over the exposedsurfaces of the fin channels 750, where the disposable spacer materialmay be a thin conformal oxide or nitride layer (e.g., SiO₂, SiN). Invarious embodiments, the disposable spacer material 1100 may be formedby an ALD or PE-ALD process. The thickness of the disposable spacermaterial 1100 at least on the sidewalls of the fin channel 750 can besufficient to extend past the thickness of the WFM cap 920 to define thethickness of a gate 1030, where for example, if the WFM cap 920 has athickness of about 7 nm in the x and y directions, then the thickness ofthe disposable spacer material 1100 is in the range of about 9 to about12 nm, so the thickness of the gate may be in the range of about 2 nm toabout 5 nm. In various embodiments, the thickness of the disposablespacer caps 1120 is greater than the thickness of the work functionmetal cap 920, so an overhang extending horizontally over the gateprecursor(s) 1020 is formed. In various embodiments, the thickness ofthe deposited disposable spacer material 1100 may be in the range of 2nm to 3 nm greater than the thickness of the WFM caps 920.

FIG. 29 is an enlarged inset view of a substrate with a disposablespacer forming an electronic device structure according to an exemplaryembodiment. The diagram shows a cross-sectional view illustrating the xand z directions of the device structure.

The disposable spacer material 1100 on the gate precursor 1020 surfacesmay be removed to expose at least a portion of the gate precursors 1020between the fin channels 750, while leaving the disposable spacermaterial on the side walls of the fin channels 750. The disposablespacer material 1100 is removed from the horizontal surfaces between thevertical fin channels 750 to form disposable spacer caps 1120 over theexposed surfaces of the vertical fin channels 750. The disposable spacercaps 1120 may be masks for subsequent etching of at least a portion ofgate precursors 1020 to form gates 1030.

FIG. 30 is an enlarged inset view of a substrate with a disposablespacer forming an electronic device structure according to an exemplaryembodiment. The diagram shows a cross-sectional view illustrating the xand z directions of the device structure.

In one or more embodiments, the portion of the gate precursors 1020exposed between the disposable spacer caps 1120 may be removed, forexample by RIE, to form gates 1030, where the gates 1030 may have athickness in the range of about 2 nm to about 5 nm, or in the range ofabout 2 nm to about 3 nm. Gates 1030 may be formed adjacent to the workfunction metal cap 920, where the gates 1030 may form an interface withthe gate metal layer of the WFM cap 920, and where the gate metal layermay be a metal nitride layer. The exposed portion of the gate precursors1020 may be removed down to the surface of the first low-k dielectricspacers 820, where the material of the first low-k dielectric spacers820 may act as an etch stop. In various embodiments, gates 1030 may havea height in the z direction of about 20 nm to about 300 nm, or about 50nm to about 200 nm, or about 75 nm to about 100 nm, where the height ofthe gates 1030 is less than the height of the WFM cap 920 and finchannels 750.

FIG. 31 is an enlarged inset view of a substrate with an exposed finchannel and a gate structure forming an electronic device structureaccording to an exemplary embodiment. The diagram shows across-sectional view illustrating the x and z directions of the devicestructure.

In various embodiments, the disposable spacer caps 1120 may be removedto expose the distal end portion of the fin channels 750, where thedisposable spacer caps 1120 may be removed by etching. The gate 1030 andWFM cap 920 form a gate structure with the fin channel 750 for controlof current through the fin channel 750, where the gate structure may beon four sides and surround the fin channel 750. In various embodiments,the gate structure may have a height in the range of about 20 nm toabout 300 nm, or about 50 nm to about 200 nm, or about 75 nm to about100 nm.

FIG. 32 is an enlarged inset view of a substrate with a gate structureand low-k dielectric material forming an electronic device structureaccording to an exemplary embodiment. The diagram shows across-sectional view illustrating the x and z directions of the devicestructure.

In various embodiments, a second low-k dielectric material 1200 may beformed over the exposed distal end portion of the fin channels 750 andin the spaces between the gates 1030. In various embodiments, the secondlow-k dielectric material 1200 may be the same as the first low-kdielectric material 800 formed adjacent to the first drain 400 and thesecond drain 600. The second low-k dielectric material 1200 may be anoxide. In various embodiments, the second low-k dielectric material 1200may be conformally deposited.

FIG. 33 is an enlarged inset view of a substrate with a gate structureand low-k dielectric material forming an electronic device structureaccording to an exemplary embodiment. The diagram shows across-sectional view illustrating the x and z directions of the devicestructure.

The second low-k dielectric material 1200 may be removed by etching orchemical-mechanical polishing to the level of the top of the finchannels 750 to form second low-k dielectric spacers 1220 between thefin channels 750. The second low-k dielectric spacers 1220 may isolatethe fin channels from each other and the other neighboring components.In various embodiments, the second low-k dielectric spacers 1220 may bemade of the same material as the first low-k dielectric spacers 820,where the first low-k dielectric spacers 820 and second low-k dielectricspacers 1220 can have essentially the same electrical properties.

FIG. 34 is a diagram of a substrate with low-k dielectric spacers andexposed fin channels of an electronic device structure according to anexemplary embodiment. The diagram shows a cross-sectional viewillustrating the x and z directions of the device structure.

The height of the second low-k dielectric spacers 1220 may be reduced toexpose a portion of the distal end of the fin channels 750. The heightof the second low-k dielectric spacers 1220 may be reduced by etching.

FIG. 35 is a diagram of a substrate with an inter-layer dielectric of anelectronic device structure according to an exemplary embodiment. Thediagram shows a cross-sectional view illustrating the x and z directionsof the device structure.

An inter-layer dielectric (ILD) material layer 1300 may be formed overthe distal end of the fin channels 750 to provide electrical insulationbetween the fin channels 750. In various embodiments, the inter-layerdielectric is SiO₂. In various embodiments, the inter-layer dielectricis not Si₃N₄. The SiO₂ may be deposited over the second low-k dielectricspacers 1220 and the exposed portions of the distal end of the finchannels 750, where the ILD material layer 1300 may be conformallydeposited. A portion of the inter-layer dielectric (ILD) material layer1300 may be removed by chemical-mechanical polishing to provide a flat,uniform surface, where the top surface of the inter-layer dielectric(ILD) material layer 1300 may be coplanar with the tops of the finchannels 750. In various embodiments, the ILD material is different fromthe material of the second low-k dielectric spacers 1220.

FIG. 36 is a diagram of a substrate with an inter-layer dielectric andhardmask of an electronic device structure according to an exemplaryembodiment. The diagram shows a cross-sectional view illustrating the xand z directions of the device structure.

A hardmask 1400 may be formed over the inter-layer dielectric materiallayer 1300. The hardmask may be titanium nitride (TiN), SiO₂, Al₂O₃,silicon nitride (SiN), or combinations thereof. In various embodiments,the hardmask 1400 is SiN.

FIG. 37 is a diagram of a substrate with an inter-layer dielectric and apartially removed hardmask of an electronic device structure accordingto an exemplary embodiment. The diagram shows a cross-sectional viewillustrating the x and z directions of the device structure.

A portion of the hardmask 1400 may be removed to expose the tops of thefin channels 750 and inter-layer dielectric material layer 1300, wherethe hardmask may be removed by masking and/or etching. The exposed topsof the fin channels 750 may be etched to reduce the height of the finchannels. In various embodiments, the top surface of fin channels 750may be approximately co-planar with the interface between theinter-layer dielectric material layer 1300 and second low-k dielectricspacers 1220.

FIG. 38 is a diagram of a substrate with an inter-layer dielectric andsources of an electronic device structure according to an exemplaryembodiment. The diagram shows a cross-sectional view illustrating the xand z directions of the device structure.

In various embodiments, a portion of the fin channels 750 may be removedto form openings 1310 in the inter-layer dielectric material layer 1300,where the remaining inter-layer dielectric material layer 1300 formsinter-layer dielectric spacers 1320 between the openings 1310. Portionsof the inter-layer dielectric material layer 1300 may be removed to formthe openings 1310 by masking and etching the ILD material layer, aswould be known in the art.

A source material may be formed in the openings 1310 to form firstsources 1520. In various embodiments, the first sources 1520 may beepitaxially grown on the top surface of the fin channel 750, where firstsources 1520 may have the same crystal structure and orientation as theunderlying fin channel 750. The first source may be Si, SiGe, SiC, orSiP, where the first source may be doped with boron, phosphorus, orcarbon. In various embodiments, the dopant is not arsenic. Growth of thesource material may be done as a single layer or as multiple depositedlayers having varying dopant levels. In various embodiments, the firstsource(s) 1520 have the same doping as the first drain 400. The sources1520 on each of the fin channels 750 associated with the first drain 400have the same crystal orientation as the first bottom surface 190 toprovide predetermined electrical properties (e.g., carrier mobility).

FIG. 39 is a diagram of a substrate with an inter-layer dielectric andremoved hardmask of an electronic device structure according to anexemplary embodiment. The diagram shows a cross-sectional viewillustrating the x and z directions of the device structure.

The remaining hardmask 1400 may be removed from the surface of the ILDmaterial layer 1300, for example, by selective etching.

FIG. 40 is a diagram of a substrate with an inter-layer dielectric and apartially removed hardmask of an electronic device structure accordingto an exemplary embodiment. The diagram shows a cross-sectional viewillustrating the x and z directions of the device structure.

In one or more embodiments, a new hardmask 1410 may be formed over thefirst sources 1520 and sections of ILD material layer 1300, and aportion of the hardmask 1410 removed to expose the previously unexposedtop surfaces of the fin channels 750 and inter-layer dielectric materiallayer 1300.

A portion of the fin channels 750 may be removed to form openings 1315in the inter-layer dielectric material layer 1300, where the remaininginter-layer dielectric material layer 1300 forms inter-layer dielectricspacers 1320 between the openings 1315. The exposed tops of the finchannels 750 may be etched to reduce the height of the fin channels. Invarious embodiments, the top surface of fin channels 750 may beapproximately co-planar with the interface between the inter-layerdielectric material layer 1300 and second low-k dielectric spacers 1220.

FIG. 41 is a diagram of a substrate with an inter-layer dielectric andsources of an electronic device structure according to an exemplaryembodiment. The diagram shows a cross-sectional view illustrating the xand z directions of the device structure.

Source material may be formed in the openings 1310 to form secondsources 1540. In various embodiments, the second source(s) 1540 may beepitaxially grown on the top surface of the fin channel(s) 750, wheresecond sources 1540 may have the same crystal structure and orientationas the underlying fin channel 750. The second source(s) may be Si, SiGe,SiC, or SiP, where the second source may be doped with boron,phosphorus, or carbon. In various embodiments, the dopant is notarsenic. Growth of the source material may be done as a single layer oras multiple deposited layers having varying dopant levels. In one ormore embodiments, the material of the second sources 1540 is differentthan the material of the first sources 1520. In various embodiments, thesecond source(s) 1540 have the same doping as the second drain 600. Thesources 1540 on each of the fin channels 750 associated with the seconddrain 600 have the same crystal orientation as the second bottom surface195 to provide predetermined electrical properties (e.g., carriermobility).

FIG. 42 is a diagram of a substrate with an inter-layer dielectric andremoved hardmask of an electronic device structure according to anexemplary embodiment. The diagram shows a cross-sectional viewillustrating the x and z directions of the device structure.

In various embodiments, the remaining portion of hardmask 1410 may beremoved. The exposed surface of sources 1520, sources 1540, andinter-layer dielectric spacers 1320 may be chemically-mechanicallypolished. The surface may be cleaned as known in the art.

In one or more embodiments, a complimentary pair of FETs are formed fromfirst drain 400, fin channels 750 and first source 1520, and seconddrain 600, fin channels 750, and second source 1540. In variousembodiments, first drain 400 and first source 1520 form an n-finFET withan intrinsic fin channel 750, and second drain 600 and second source1540 form a p-finFET with an intrinsic fin channel 750. Gates 1030 foreach complimentary pair of FETs may be electrically coupled.Corresponding finFETs may be coupled to form a complementary metal oxidesemiconductor (CMOS) transistor.

FIG. 43 is a top view of a substrate with a drain and a plurality of finchannels of an electronic device structure according to an exemplaryembodiment, which shows a cross-sectional view illustrating the x and ydirections of the device structure.

In one or more embodiments, a plurality of vertical fin channels 750 areepitaxially grown on a first drain 400 deposited on substrate 100. Anopening may be formed in intervening layers and filled with a conductivematerial to form a first drain contact 1600 with the first drain 400,where the first drain contact may be laterally offset from the finchannels 750.

FIG. 44 is a top view of a substrate with drain contacts, gate contacts,and source contacts of an electronic device structure according to anexemplary embodiment, which shows a cross-sectional view illustratingthe x and y directions of the device structure.

In one or more embodiments, a WFM cap 920 and a gate 1030 are formedaround the plurality of vertical fin channels 750, where the WFM cap 920and gate 1030 form a collar around the fin channel(s) 750 that covers atleast a portion of the height of the fin channel(s) 750. An opening maybe formed in intervening layers and filled with a conductive material toform a first source contact 1650 with a first source 1520 below thefirst source contact 1650. An opening may be formed in interveninglayers and filled with a conductive material to form a first gatecontact 1670, where the first gate contact 1670 may be in electricalcontact with the side walls of the gates 1030. A first gate contact 1670may be coupled with a second gate contact to form a CMOS.

FIG. 45 is a side view of a fin channel assembly with drain contacts,gate contacts, and source contacts of an electronic device structureaccording to an exemplary embodiment, which shows a cross-sectional viewillustrating the y and z directions of the device structure. Thevertical arrangement of the drain, fin channel, and source allowscurrent to flow in a direction perpendicular to the substrate throughthe finFet device. Current may pass vertically through each of thesources 1520 or 1540 to the fin channels associated with drain 400 ordrain 600 and to drain 400 or drain 600 respectively.

In one or more embodiments, the first drain contact 1600, first gatecontact 1670, and first source contact 1650 may extend vertically fromthe respective drain, source, and gate layers to a wiring level. Thecontacts may include vias filled with a conformally deposited metal toform electrical leads to the wiring level.

FIG. 46 is a side view of a fin channel assembly showing multiple layersof an electronic device structure according to an exemplary embodiment,which shows a cross-sectional view illustrating the y and z directionsof the device structure.

In one or more embodiments, the first drain contact 1600, first gatecontact 1670, and first source contact 1650 may extend verticallythrough a first low-k dielectric spacers 820, a second low-k dielectricspacer 1220, and/or an inter-layer dielectric spacer 1320 to a wiringlevel, where the filled vias may intersect with conductive trenches1690, which may be filled with a conformally deposited metal. Theconductive trenches 1690 may form electrical connections to otherdevices and components to form an integrated circuit, for example anASIC or a central processing unit (CPU).

FIG. 47 is a block/flow diagram of an exemplary method of forming avertical finFET in accordance with an illustrative embodiment.

In block 1710 of method 1700, a substrate surface is prepared forsubsequent deposition and forming steps, where the substrate may beprepared by removing a native oxide layer, cleaning to remove organicand ionic contaminants, and heat treating to provide a crystallinesurface suitable for epitaxial growth.

In block 1720, a nitride layer may be formed over at least a portion ofthe prepared substrate surface, where the nitride layer may be Si₃N₄.The nitride layer may function as a mask for subsequent etching andforming processes.

In block 1730, portions of the nitride layer may be removed by maskingand etching to reveal portions of the underlying substrate, whileleaving nitride islands over other portions of the substrate surface.

In block 1740, the revealed portions of the underlying substrate may beetched to form trenches within the substrate.

In block 1750, a dielectric material may be deposited in the trenches.The dielectric material can form shallow trench isolation regions on thesubstrate, which separate the raised substrate portions covered by thenitride islands. The deposited dielectric material may fill the trenchesand cover the nitride islands. In various embodiments, the dielectricmaterial deposited in the trenches is SiO₂, where the SiO₂ is notthermally grown.

In block 1760, the dielectric material may be chemically-mechanicallypolished to remove the portion of dielectric material extending abovethe surface of the nitride islands. The chemical-mechanical polishingmay provide a uniform planar surface that can define an initial heightfor subsequent etching and deposition processes.

In block 1770, one or more of the nitride islands exposed by thechemical-mechanical polishing may be removed to expose the underlyingsubstrate. The exposed nitride islands may be removed by a selectiveetching process, for example, a RIE and/or a phosphoric acid solutionfor Si₃N₄.

FIG. 48 is a continuation of the block/flow diagram of an exemplarymethod of forming a vertical finFET of FIG. 47 in accordance with anillustrative embodiment.

In block 1780, the height of the underlying substrate may be reduced byetching away a portion of the substrate material underlying thepreviously removed nitride island(s). A recessed region may be formed byetching a predetermined amount of substrate material, where the recessedregion has an exposed bottom surface. The exposed bottom surface of therecessed region may be above the bottom surface of the neighboring STIregions after etching is completed, so the STI regions separate therecessed regions of the substrate.

In block 1790, a first material may be deposited in the recessed regionto form a first drain for a finFET structure. The first drain may beepitaxially grown from the exposed bottom surface of the recessed regionin the substrate, so the drain has the same crystal structure andorientation as the surface of the substrate. In various embodiments, thecomposition of the substrate may be predetermined or adjusted to changethe lattice parameters of the substrate and bottom surface to controlfor crystal strain and/or defects and dislocations at the epitaxyinterface. The crystal orientation and lattice constants of thesubstrate may be predetermined to provide epitaxial growth propertiesand electrical properties (i.e., controlled lattice mismatch, strain,minimal dislocations) at the interfaces of the device components. Invarious embodiments, the drain may be an n-doped drain or a p-dopeddrain.

While various embodiments may be described as having the drain initiallyformed in the recessed regions, this is for descriptive purposes only,and in one or more embodiments the source and drain may be exchanged sothe source material is formed in the recess region.

In block 1800, a hard oxide mask may be formed over the STI regions,drains, and nitride islands.

In block 1810, the hard oxide mask may be removed from one or morenitride islands by etching.

In block 1820, the exposed nitride islands may be removed to expose theunderlying substrate.

In block 1830, the height of the underlying substrate may be reduced byetching away a portion of the substrate material underlying thepreviously removed nitride island. A recessed region may be formed byetching a predetermined amount of substrate material, where the recessedregion has an exposed bottom surface. The exposed bottom surface of therecessed region may be above the bottom surface of the neighboring STIregions after etching is completed, so the STI regions separate therecessed regions of the substrate.

In block 1840, a second material may be deposited in the recessed regionto form a second drain for a finFET structure. The second drain may beepitaxially grown from the exposed bottom surface of the recessed regionin the substrate, so the drain has the same crystal structure andorientation as the surface of the substrate. In various embodiments, thecomposition of the substrate may be predetermined or adjusted to changethe lattice parameters of the substrate and bottom surface to controlfor crystal strain and/or defects and dislocations at the epitaxyinterface. In various embodiments, the drain may be an n-doped drain ora p-doped drain. The second material may be the same as or differentthan the first material.

FIG. 49 is a continuation of the block/flow diagram of an exemplarymethod of forming a vertical finFET of FIG. 48 in accordance with anillustrative embodiment.

In block 1850, the hard oxide mask over the previously formed drains andSTI regions may be removed to reveal the underlying features. Afterremoval of the hard oxide mask, all of the top surfaces of the drainsare exposed for subsequent processes.

In block 1860, a channel material is formed on the exposed drainsurfaces. The channel material may be epitaxially grown from the exposeddrain surfaces, so the channel material has the same crystal structureand orientation as the surface of the drain. In various embodiments, thechannel material is an intrinsic silicon (Si), whereas the drain is anextrinsic material. The channel material may be epitaxially grown to aheight greater than the height of the dielectric material of theneighboring STI regions.

In block 1870, portions of the channel material may be removed to formpillars of channel material separated by troughs, where the troughsextend to the surface of the drain from which the channel material wasgrown. The separation of the pillars of channel material by the troughsforms one or more fin channels extending from the underlying drain. Invarious embodiments, from 1 to 25 fin channels may be formed on eachdrain based on a predetermined current carrying capacity of the finalfinFET.

In block 1880, a low-k spacer material may be formed over the finchannels and in the troughs. The low-k spacer material may beconformally deposited over the fin channels and in the troughs to ensurethe troughs are essentially completely filled, although, for example,unintended voids and uncovered surfaces may unintentionally occur. Thelow-k spacer material may be deposited by ALD, PE-ALD, CVD, PE-CVD, or acombination thereof. In various embodiments, the low-k spacer materialmay be SiBCN, SiOCN, SiN or combinations thereof.

In block 1890, the deposited low-k spacer material may bechemically-mechanically polished to remove the portion of low-k spacermaterial extending above the top surface of the fin channels. Thechemical-mechanical polishing may provide a uniform planar surface thatcan define a uniform initial height for subsequent etching anddeposition processes.

In block 1900, the height of the low-k spacer material in the troughsand adjacent to the fin channels may be reduced by removing a thicknessof the low-k spacer material to a predetermined depth. The predetermineddepth may be approximately even with the top surfaces of the SiO₂forming the STI regions, so a uniform surface height is available forsubsequent depositions and etchings.

In block 1910, a multi-layer work function metal layer is formed overthe top and side surfaces of the fin channels exposed after removal ofthe low-k spacer material. At least one high-k dielectric material layermay first be formed directly on the top and side surfaces of the finchannels to electrically insulate the fin channels, where the high-kdielectric material may be a high-k oxide material. Additional high-kdielectric material layer(s) having different chemical compositions andproperties may be also be deposited, for example a layer of HfO₂ and alayer of HfSiO₄ may be deposited to control interfacial properties. Atleast one metal nitride layer is formed over the high-k dielectricmaterial layer to form a contact interface for a gate material and tocontrol the work function of the interface. The WFM layer materials andgate material may be predetermined to achieve intended electricalproperties of the finFET device, for example, capacitive coupling andcurrent-voltage characteristics.

FIG. 50 is a continuation of the block/flow diagram of an exemplarymethod of forming a vertical finFET of FIG. 49 in accordance with anillustrative embodiment.

In block 1920, the portion of the WFM layer on the top surface of thefin channels may be removed to expose the top surfaces of the finchannels.

In block 1930, a gate material may be formed over the fin channels andWFM layer, and fill in the troughs between the WFM layers covering thesides of the fin channels. The gate material may be conformallydeposited to ensure the troughs are essentially completely filled and auniform interface is achieved between the WFM layer and the gatematerial. In various embodiments, the gate material is tungsten.

In block 1940, the gate material may be chemically-mechanically polishedto remove the portion of gate material extending above the top surfaceof the fin channels. The chemical-mechanical polishing may provide auniform planar surface that can define a uniform initial height forsubsequent etching and deposition processes. The WFM layers and gatematerial may extend from the low-k spacer material to the top surfacesof the fin channels.

In block 1950, the height of the gate material may be reduced byremoving a portion of the gate material to form gate precursors. Theheight of the fin channel covered by the remaining gate materialdetermines the height of the gate.

In block 1960, the WFM layers on the sides of the fin channels may beremoved to expose a portion of the fin channels. The metal nitride layerand high-k dielectric material layer of the WFM layer may be removed byone or more etching processes. The WFM layers and gate precursors mayhave the same height.

In block 1970 a disposable spacer material is formed over the exposedtop and side surfaces of the fin channels, and the exposed surfaces ofthe WFM layer and gate precursors. The thickness of the disposablespacer material may be precisely controlled, for example, within oneatomic layer by an ALD deposition to define a width of a subsequentlyformed gate, where the disposable spacer material is conformallydeposited on the exposed top and side surfaces of the fin channels.

In block 1980, the horizontal portion of the disposable spacer materialcovering only the gate material of the gate precursors is removed, whilethe disposable spacer material covering the top and side surfaces of thefin channels remains to create a disposable spacer cap. Masking and/orRIE may be used to selectively etch the disposable spacer material onthe top surface of the gate precursors. After etching, the gate materialbetween disposable spacer cap is exposed for subsequent removal.

FIG. 51 is a continuation of the block/flow diagram of an exemplarymethod of forming a vertical finFET of FIG. 50 in accordance with anillustrative embodiment.

In block 1990, the exposed gate material of the gate precursors isremoved to expose the low-k spacer and create two gates separated by atrough. The low-k spacer electrically insulates the gates from thedrain.

In block 2000, the disposable spacer caps are removed from the finchannels. WFM layers and gates of a predetermined height are at least onopposite sides of each fin channel. In various embodiments, the WFMlayers and gates are on four sides of the fin channel, where a channelcurrent may be pinched off by a gate voltage, as compared to a MOSFETchannel lacking a gate on at least one side.

In block 2010, a low-k spacer material may be formed over the finchannels, WFM layer, and gates, and fill in the troughs between thegates. The low-k spacer material may be conformally deposited to ensurethe troughs between the gates are essentially completely filled. Invarious embodiments, the low-k spacer material may be SiBCN, SiOCN, SiNor combinations thereof.

In block 2020, the low-k spacer material may be chemically-mechanicallypolished to remove the portion of low-k spacer material extending abovethe top surface of the fin channels. The chemical-mechanical polishingmay provide a uniform planar surface that can define a uniform initialheight for subsequent etching and deposition processes.

In block 2030, the low-k spacer material may be removed to apredetermined depth below the tops of the of the fin channels. The low-kspacer material may be etched.

In block 2040, an interlayer dielectric is deposited on the exposed finchannels and exposed surface of the low-k spacer material, where the ILDcan be SiO₂.

In block 2050, the ILD is chemically-mechanically polished to form auniform planar surface.

FIG. 52 is a continuation of the block/flow diagram of an exemplarymethod of forming a vertical finFET of FIG. 51 in accordance with anillustrative embodiment.

In block 2060, a first hardmask is deposited on the ILD and the topsurfaces of the fin channels.

In block 2070, a portion of the first hardmask is removed from selectedareas of the ILD to expose one or more top surfaces of fin channels.

In block 2080, fin channel material is removed to form openings in theILD. The height of the fin channels may be reduced to the level of thetop surface of the low-k spacer.

In block 2090, a material for forming the source of the finFET may bedeposited in the openings in the ILD. The source material may beepitaxially grown from the fin channel, and have the same crystalstructure and orientation as the fin channel material.

In block 2100, the first hardmask remaining on the surface of the ILD isremoved.

In block 2110, a second hardmask is deposited on the surface of the ILD,the previously deposited sources, and the exposed tops of the finchannels.

In block 2120, the second hardmask is removed from selected areas of theILD to expose one or more top surfaces of fin channels.

FIG. 53 is a continuation of the block/flow diagram of an exemplarymethod of forming a vertical finFET of FIG. 52 in accordance with anillustrative embodiment.

In block 2130, fin channel material is removed to form openings in theILD. The height of the fin channels may be reduced to the level of thetop surface of the low-k spacer.

In block 2140, a material for forming the source of the finFET may bedeposited in the openings in the ILD. The source material may beepitaxially grown from the fin channel, and have the same crystalstructure and orientation as the fin channel material. The sources oneach of the fin channels associated with the first drain and the seconddrain have the same crystal orientation as the fin channels.

In block 2150, the second hardmask remaining on the surface of the ILDis removed.

In various embodiments, openings can be made in intervening layers toform vias that may be filled with a conductive material to formelectrical contacts with the source, drain and gate. The vias may befilled by depositing one or more conformal layers and electrodepositinga metal in the vias on the conformal layer.

An aspect of the disclosure relates to a method of fabricating avertical field effect transistor, the method comprising forming a firstrecess in a substrate with a predetermined crystal orientation, whereinthe first recess has a first bottom surface; growing a first drainepiaxially from the bottom surface of the first recess; forming a secondrecess in the substrate, wherein the second recess has a second bottomsurface; growing a second drain epiaxially from the bottom surface ofthe second recess; growing a channel material epitaxially on the firstdrain and the second drain; forming troughs in the channel material toform one or more fin channels on the first drain and one or more finchannels on the second drain, wherein the troughs over the first drainextend to the surface of the first drain, and the troughs over thesecond drain extend to the surface of the second drain; forming a WFMcap on each of the fin channels; forming a gate on each of the WFM caps,wherein the WFM cap electrically separates the gate from the finchannel; growing a first source epitaxially on each of the fin channelsgrown on the first drain; and growing a second source epitaxially oneach of the fin channels grown on the second drain.

An aspect of the disclosure also relates to a vertical field effecttransistor comprising a first recess in a substrate with a predeterminedcrystal orientation, wherein the first recess has a first bottomsurface; a first drain on the bottom surface of the first recess,wherein the first drain has the same crystal orientation as the firstbottom surface; a second recess in the substrate, wherein the secondrecess has a second bottom surface; a second drain on the bottom surfaceof the second recess, wherein the second drain has the same crystalorientation as the second bottom surface; one or more fin channels onthe first drain, wherein the one or more fin channels on the first drainhave the same crystal orientation as the first bottom surface; one ormore fin channels on the second drain, wherein the one or more finchannels on the second drain have the same crystal orientation as thesecond bottom surface; a WFM cap on each of the fin channels; a gate oneach of the WFM caps, wherein the WFM cap electrically separates thegate from the fin channel; a first source on each of the fin channelsgrown on the first drain, wherein the first source has the same crystalorientation as the first bottom surface; and a second source on each ofthe fin channels grown on the second drain, wherein the second sourcehas the same crystal orientation as the second bottom surface.

Having described preferred embodiments of vertical transistorfabrication and devices (which are intended to be illustrative and notlimiting), it is noted that modifications and variations can be made bypersons skilled in the art in light of the above teachings. It istherefore to be understood that changes may be made in the particularembodiments disclosed which are within the scope of the invention asoutlined by the appended claims. Having thus described aspects of theinvention, with the details and particularity required by the patentlaws, what is claimed and desired protected by Letters Patent is setforth in the appended claims.

What is claimed is:
 1. A method of fabricating a vertical field effecttransistor comprising: forming a first recess in a substrate, whereinthe first recess has a first bottom surface; epitaxially growing a firstdrain from the first bottom surface of the first recess; epitaxiallygrowing a second drain from the second bottom surface of a second recessformed in the substrate; epitaxially growing a channel material on thefirst drain and the second drain; forming troughs in the channelmaterial to form one or more fin channels on the first drain and one ormore fin channels on the second drain, wherein the troughs over thefirst drain extend to the surface of the first drain, and the troughsover the second drain extend to the surface of the second drain; forminga gate structure on each of the one or more fin channels; and growingsources on each of the fin channels associated with the first and seconddrains.
 2. The method of claim 1 further comprising forming a shallowtrench isolation region in the substrate, wherein the shallow trenchisolation region is between the first drain and the second drain, andforming a first low-k dielectric spacer in each of the troughs betweenthe fin channels.
 3. The method of claim 1 further comprising forming afirst drain contact to the first drain, forming a first gate contact tothe first gate, and forming a first source contact to each of thesource(s) on the fin channels associated with the first drain.
 4. Themethod of claim 1, wherein from 1 to 25 fin channels are formed on thefirst drain, and from 1 to 25 fin channels are formed on the seconddrain.
 5. The method of claim 1, wherein the fin channels have a heightin the range of about 30 nm to about 400 nm, and the fin channelscomprise intrinsic silicon.
 6. The method of claim 1, wherein the firstdrain and the sources on the fin channels associated with the firstdrain comprise an n-doped material, and the second drain and sources onthe fin channels associated with the second drain comprise a p-dopedmaterial.
 7. The method of claim 1, wherein the gate structure compriseswork function metal (WFM) caps formed on the fin channels by atomiclayer deposition (ALD) or plasma-enhanced atomic layer deposition(PE-ALD).
 8. The method of claim 7, wherein each of the WFM caps isformed to a thickness in the range of about 5 nm to about 15 nm, and thegate on each of the WFM caps is formed to a thickness in the range ofabout 2 nm to about 5 nm.
 9. A method of fabricating a vertical fieldeffect transistor comprising: forming a shallow trench isolation regionin a substrate; forming a first recess in a substrate, wherein the firstrecess has a first bottom surface; epitaxially growing a first drainfrom the first bottom surface of the first recess; epitaxially growing asecond drain from the second bottom surface of a second recess formed inthe substrate, wherein the shallow trench isolation region is betweenthe first drain and the second drain; growing a channel materialepitaxially on the first drain and the second drain, wherein the channelmaterial comprises intrinsic silicon; forming troughs in the channelmaterial to form one or more fin channels on the first drain and one ormore fin channels on the second drain, wherein the troughs over thefirst drain extend to the surface of the first drain, and the troughsover the second drain extend to the surface of the second drain; forminga first low-k dielectric spacer in each of the troughs between the finchannels; forming a gate structure on each of the one or more finchannels; and growing sources on each of the fin channels associatedwith the first and second drains.
 10. The method of claim 9, wherein thefin channels have a height in the range of about 30 nm to about 400 nm,and the fin channels comprise intrinsic silicon.
 11. The method of claim9, wherein the gate structure has a height in the range of about 20 nmto about 300 nm.
 12. The method of claim 9, wherein each gate structureon each of the one or more fin channels comprises a WFM cap formed to athickness in the range of about 5 nm to about 15 nm, and a gate on eachof the WFM caps formed to a thickness in the range of about 2 nm toabout 5 nm.
 13. The method of claim 12, wherein the gate comprisestungsten.